id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36259	`_is_pk_set()` is incorrectly used to check for unsaved models.	Clifford Gama	Clifford Gama	"Since models defined with custom primary keys can have `pk` set before being saved to the database, this means they bypass this as if they were saved. Here is an example:
{{{#!diff
diff --git a/tests/one_to_one/tests.py b/tests/one_to_one/tests.py
index 451e97c274..67b1c32e90 100644
--- a/tests/one_to_one/tests.py
+++ b/tests/one_to_one/tests.py
@@ -170,6 +170,16 @@ class OneToOneTests(TestCase):
         with self.assertRaises(Restaurant.DoesNotExist):
             place.restaurant
 
+    def test_unsaved_object_with_supplied_primary_key(self):
+        link1 = Place.objects.create(name=""Ushaka"", address=""Ethekwini"")
+        link2 = ManualPrimaryKey(primary_key=""YTREWQ"", name=""moonwalk"")
+        msg = (
+            ""save() prohibited to prevent data loss due to unsaved related object ""
+            ""'link2'.""
+        )
+        with self.assertRaisesMessage(ValueError, msg):
+            MultiModel.objects.create(link1=link1, link2=link2, name=""Unsavable"")
+
     def test_reverse_relationship_cache_cascade(self):
         """"""
         Regression test for #9023: accessing the reverse relationship shouldn't
}}}

which results in
{{{#!python
FE
======================================================================
ERROR: test_unsaved_object_with_supplied_primary_key (one_to_one.tests.OneToOneTests.test_unsaved_object_with_supplied_primary_key)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/home/clifford/code/django/django/db/backends/sqlite3/base.py"", line 304, in check_constraints
    raise IntegrityError(
django.db.utils.IntegrityError: The row in table 'one_to_one_multimodel' with primary key '1' has an invalid foreign key: one_to_one_multimodel.link2_id contains a value 'YTREWQ' that does not have a corresponding value in one_to_one_manualprimarykey.primary_key.

======================================================================
FAIL: test_unsaved_object_with_supplied_primary_key (one_to_one.tests.OneToOneTests.test_unsaved_object_with_supplied_primary_key)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/home/clifford/code/django/tests/one_to_one/tests.py"", line 180, in test_unsaved_object_with_supplied_primary_key
    with self.assertRaisesMessage(ValueError, msg):
  File ""/usr/lib/python3.12/contextlib.py"", line 144, in __exit__
    next(self.gen)
AssertionError: ValueError not raised

----------------------------------------------------------------------
Ran 1 test in 0.004s

FAILED (failures=1, errors=1)
}}}
And here is the culprit [https://github.com/django/django/blob/ef6a83789b310a441237a190a493c9586a4cb260/django/db/models/base.py#L1220C17-L1224C22 code]:
This is done in a few other places. My proposal is to replace such uses cases of `_is_pk_set` with `instance._state.added` checks. "	Bug	assigned	Database layer (models, ORM)	dev	Release blocker		_is_pk_set		Unreviewed	0	0	0	0	0	0